\documentclass[tikz]{standalone}

\usepackage{tkz-euclide}
\usepackage{physics}

\begin{document}
\begin{tikzpicture}[scale=4]
  \tkzInit[xmax=1,ymax=1,ymin=-1,xmin=-1]
  \tkzDrawX[right space=0.2, left space=0.2,label={}]
  \tkzDrawY[up space=0.2, down space=0.2, label={}]
  \tkzDefPoint(0,0){orig}
  \tkzDefPoint(1,0){b0}
  \tkzDefPoint(0,1){b1}
  \tkzDefPoint(0.3,0){p0}
  \tkzDefPoint(0,0.7){p1}
  \tkzDefPoint(0.3,0.7){b}
  \tkzDefPoint(0.5477,-0.8367){kb}
  \tkzDefPoint(0.5477,0){a0}
  \tkzDefPoint(0,-0.8367){a1}
  \tkzDrawCircle[thick,gray](orig,b0)
  \tkzLabelPoint(b0){$\ket{0}$}
  \tkzLabelPoint[left](b1){$\ket{1}$}

  \tkzDrawSegment[thick,gray](b0,b1) 
  \tkzLabelSegment[right,gray](b0,b1){$\mathbf{B}^1$}

  \tkzDrawSegment[-stealth](orig,kb)
  \tkzDrawSegment[dashed](a0,kb)
  \tkzLabelPoint(a0){$\alpha_0$}
  \tkzDrawSegment[dashed](a1,kb)
  \tkzLabelPoint(a1){$\alpha_1$}
  \tkzLabelSegment(orig,kb){$\ket{b}$}

  \tkzDrawSegment[-stealth](orig,b)
  \tkzLabelSegment(orig,b){$\mathbf{b}$}

  \tkzDrawSegment[dashed](p0,b)
  \tkzDrawSegment[dashed](p1,b) 
  \tkzLabelSegment[right](p0,b){$\alpha_0^2$}
  \tkzLabelSegment[below](p1,b){$\alpha_1^2$}


  \tkzDrawPoints(b0,b1,b,kb)
\end{tikzpicture}
\end{document}